This invention relates to an internally-grooved heat exchanger tube for use in a heat exchanger of a refrigerating machine and an air conditioning machine or the like, and a metal strip machining roll for machining a metal strip for such an internally-grooved heat exchanger tube by means of rolling.
More specifically, the present invention relates to an internally-grooved heat exchanger tube structured such that the internal surface of a metal tube is divided into a plurality of continuous areas parallel to the axial direction of the tube, and fine parallel fins different in fin pattern (i.e., a fin lead angle to the axial direction of the tube, a fin vertical angle and a fin pitch or the like) are respectively formed in the adjacent areas, and a metal strip machining roll suitably used for machining a metal strip for such a heat exchanger tube by means of rolling.
In Japanese Patent Laid-open Nos. 3-13796 and 4-158193, for instance, there is provided an internally-grooved heat exchanger tube structured such that the internal surface of a metal tube is divided into a plurality of continuous areas parallel to the axial direction of the tube, and a large number of fins different in fin pattern are respectively formed in the adjacent areas.
A description will now be given of the internally-grooved heat exchanger tube disclosed in the above Japanese Patent Laid-open No. 3-13796 with reference to FIG. 19.
The internal surface of a metal tube 1 is divided into a plurality of continuous areas W1, W2, W1, W2 parallel to the axial direction L of the tube, and a large number of fine parallel fins 10, 11 respectively having the reversed lead angles xcex8, xcex8xe2x80x2 to the axial direction L of the tube are formed in the adjacent areas W1, W2.
In manufacture of the internally-grooved heat exchanger tube shown in FIG. 19, a belt-like metal strip 1a of a certain width made of copper or copper alloy, for instance, needs to be rolled in the manner of passing such a metal strip through a gap between a machining roll 3 shown in FIG. 20 and a support roll (not shown) having a flat surface pressed against the machining roll 3.
The machining roll 3 is equivalent to a roll of a predetermined length formed by combining a plurality of discshaped roll pieces 3a, 3b, 3a, 3b of a predetermined thickness together in layers parallel to the axial direction, and a large number of fine parallel grooves 30, 31 respectively having the reversed lead angles xcex81, xcex81xe2x80x2 to the axial direction are formed densely on the outer surfaces of the adjacent roll pieces 3a, 3b. 
Thus, the large number of fins 10, 11 described above are respectively formed on one surface of the rolled metal strip 1a shown in FIG. 19 in the manner of transferring the large number of grooves 30, 31 of the machining rolls 3a, 3b to one surface of the rolled metal strip.
Subsequently, the metal strip 1a is formed in a tubular shape by the steps of setting the metal strip in an electro-uniting device (not shown) with the fin-formed surface turned to the inside, then rounding the metal strip in the cross direction in the manner of passing the metal strip through a gap between each pair of forming rolls (not shown) installed in the electro-uniting device in multiple stages, and welding the butted ends in the cross direction together.
Further, the tubular molding is formed into the metal tube 1 as shown in FIG. 19 by the steps of removing a weld bead portion from the tubular molding, and subjecting the tubular molding to sinking by a predetermined drawing device to reduce the diameter of the tubular molding to a predetermined size.
According to the heat exchanger tube shown in FIG. 19, in the case of letting the refrigerant flow toward an upper portion in the tube in FIG. 19, for instance, the refrigerant flows toward each boundary portion axe2x80x2 between the adjacent areas W1, W2 while being guided by the fins 10, 11, and the collision between the flows of refrigerant occurs in each boundary portion axe2x80x2 to form a turbulent flow, so that this turbulent flow makes it possible to prevent the temperature gradient from being caused in the refrigerant, resulting in the improvement in tube heat transfer performance.
In the case of incorporating the heat exchanger tube of the prior art described above into a heat exchanger, this heat exchanger tube accelerates the formation of the turbulent flow of refrigerant in the boundary portions axe2x80x2 to permit the improvement in heat transfer performance.
However, since the boundary portions axe2x80x2 run parallel to the axial direction L of the tube, and the interference between the turbulent flows respectively formed in the boundary portions axe2x80x2 before and behind the flowing direction of refrigerant occurs to thereby cancel the effects of turbulent flow each other, the sufficient heat transfer performance could not be improved.
Further, while the heat exchanger tube of the prior art may eliminate the temperature gradient parallel to the axial direction L of the tube, the temperature gradient is easily caused parallel to the peripheral direction by this heat exchanger tube, and as a result, there is a problem in that it is not possible to sufficiently improve the heat transfer performance.
An object of the present invention is to provide an internally-grooved heat exchanger tube, which makes it possible to greatly improve the tube heat transfer performance by restraining the turbulent flows of refrigerant flowing in the axial direction of the tube from interfering with each other in a boundary portion between the adjacent areas W1, W2, while sequentially guiding a turbulent-flow formed portion of the refrigerant toward the inner peripheral side of the tube.
Another object of the present invention is to provide a metal strip machining roll, which may smoothly machine a metal strip for the internally-grooved heat exchanger tube capable of achieving the above object.
For solving the above problems, an internally-grooved heat exchanger tube according to the present invention has the following structure.
That is, an internally-grooved heat exchanger tube in the first mode according to the present invention is characterized in that the internal surface of a metal tube 1 is divided into a plurality of continuous areas W1, W2 parallel to the axial direction L of the tube, a large number of fine parallel fins 10, 11 are respectively formed in the adjacent areas W1, W2, the fins 10 in one area W1 out of the adjacent areas and the fins 11 in the other area W2 are different in at least one selected among lead angle xcex8, xcex8xe2x80x2 to the axial direction L of the tube, fin vertical angle xcex1, xcex1xe2x80x2 and fin pitch p, pxe2x80x2, and a boundary portion a between at least one area W1 and the other area W2 adjacent to the one area W1 is formed in the state of meandering to the axial direction L of the metal tube 1.
An internally-grooved heat exchanger tube in the second mode according to the present invention is characterized in that, in the internally-grooved heat exchanger tube in the first mode, the fins 10 formed in one area W1 out of the adjacent areas and the fins 11 formed in the other area W2 have the reversed lead angles xcex8, xcex8xe2x80x2 to the axial direction L of the tube.
An internally-grooved heat exchanger tube in the third mode according to the present invention is characterized in that, in the internally-grooved heat exchanger tube in the second mode, the lead angle xcex8 of each fin 10 in one area W1 out of the adjacent areas ranges from 15xc2x0 to 50xc2x0, while the lead angle xcex8xe2x80x2 of each fin 11 in the other area W2 ranges from xe2x88x9215xc2x0 to xe2x88x9250xc2x0.
An internally-grooved heat exchanger tube in the fourth mode according to the present invention is characterized in that, in the internally-grooved heat exchanger tube in the first or second mode, the boundary portion a between the adjacent areas W1, W2 is formed in the state of meandering to the axial direction L of the tube at a certain meandering pitch P, and the meandering pitch P is 8 to 60 times as large as a cross-sectional peripheral length W of the metal tube 1.
An internally-grooved heat exchanger tube in the fifth mode according to the present invention is characterized in that, in the internally-grooved heat exchanger tube in the first or second mode, each of the fins 10, 11 in the adjacent areas W1, W2 is substantially acute triangular in cross section, and a vertical angle xcex1 of each of the fins 10, 11 ranges from 10xc2x0 to 30xc2x0.
An internally-grooved heat exchanger tube in the sixth mode according to the present invention is characterized in that, in the internally-grooved heat exchanger tube in the first or second mode, a height h of each of the fins 10, 11 in the adjacent areas W1, W2 is {fraction (1/15)} to {fraction (1/70)} as small as an outside diameter R of the metal tube 1.
For solving the above problems, a metal strip machining roll for an internally-grooved heat exchanger tube in the first mode according to the present invention comprises a roll of a predetermined length formed by combining a plurality of roll pieces 2a, 2b together in layers parallel to the axial direction, wherein a large number of fine parallel grooves 20, 21 are respectively formed on the outer surfaces of the adjacent roll pieces 2a, 2b, the grooves 20 on one roll piece 2a out of the adjacent roll pieces and the grooves 21 on the other roll piece 2b are different in at least one selected among lead angle xcex81, xcex81xe2x80x2 to the axial direction, bottom angle xcex11, xcex11xe2x80x2 and groove pitch p1, p1xe2x80x2, and a contact surface c of at least one roll piece 2a with the other roll piece 2b adjacent to the roll piece 2a forms a surface inclined at a predetermined inclination angle to the axial direction of each of the roll pieces 2a, 2b. 
For solving the above problems, a metal strip machining roll for an internally-grooved heat exchanger tube in the second mode according to the present invention comprises a roll of a predetermined length formed by combining a plurality of roll pieces 2a, 2b together in layers parallel to the axial direction, wherein a large number of fine parallel grooves 20, 21 are respectively formed on the outer surfaces of the adjacent roll pieces 2a, 2b, the grooves 20 on one roll piece 2a out of the adjacent roll pieces and the grooves 21 on the other roll piece 2b are different in at least one selected among lead angle xcex81, xcex81xe2x80x2 to the axial direction, bottom angle xcex11, xcex11xe2x80x2 and groove pitch p1, p1xe2x80x2, and a contact surface c of at least one roll piece 2a with the other roll piece 2b adjacent to the roll piece 2a is composed of a plurality of continuous surfaces respectively inclined at different inclination angles to the axial direction of each of the roll pieces 2a, 2b.